Lubricant compositions

ABSTRACT

SYNTHETIC ESTER BASED LUBRICANT COMPOSITIONS CONTAINING MINOR AMOUNTS EACH OF AN N-SUBSTITUTED PHENOTHIAZINE AND A SYMMETRICAL OR ASYMMETRICAL SUBSTITUTED TRIAZINE HAVE GOOD OXIDATION STABILITY OVER A WIDE RANGE OF TEMPERATURES.

United States Patent 3,642,630 LUBRICANT COMPOSITIONS Alexander C. B.MacPhail, Wood River, 11]., and Ian Keddie, Pensby, Wirral, England,assignors to Shell Oil Company, New York, NY.

N0 Drawing. Filed Feb. 24, 1969, Ser. No. 801,785 Claims priority,application Great Britain, Feb. 22, 1968, 8,660/68 Int. Cl. Cltlm 1/38US. Cl. 252--47.5 7 Claims ABSTRACT OF THE DISCLOSURE Synthetic esterbased lubricant compositions containing minor amounts each of anN-su'bstituted phenothiazine and a symmetrical or asymmetricalsubstituted triazine have good oxidation stability over a wide range oftemperatures.

BACKGROUND OF THE INVENTION This invention relates to synthetic esterlubricating oils having exceptional oxidation stability. Moreparticularly it relates to synthetic ester oils containing N-substitutedphenothiazines and symmetrical or asymmetrical substituted triazines.

Synthetic lubricants have gained recent prominence in the field oflubrication because of stringent requirements of long life under extremeconditions imposed by certain new applications. Synthetic lubricantshave low pour points and desirable viscosity characteristics and cangenerally be used at temperatures considerably above the decompositiontemperature of most mineral oils. These oils have found use in jetaircraft, missiles, and the like Where wide temperature ranges andextreme operating conditions are likely to be encountered. Properlubrication of aircraft gas turbines, for example, requires ability tofunction at bulk oil temperatures as low as -65 F. to as high as 450 to500 F. for said applications.

Although these synthetic lubricants are more stable than mineral oils,they nevertheless undergo oxidation when exposed to air, especially whensubjected to elevated temperatures such as occur under normal operation.Oxidation stability is further impaired by dissolution of metals underoperating conditions. Dissolved metals seem to catalyze oxidativedegradation of the lubricant, thereby substantially shortening itsuseful life. Additives have traditionally been employed in smallconcentrations to impart resistance to oxidation to these lubricants.Much research effort has been directed to finding additives orcombinations of additives which are effective antioxidants for longperiods of time yet which do not impart or cause undesirable sideeffects such as increased corrosion, viscosity change, discoloration,and so on. Available information regarding mineral oil formulation isgenerally of little aid in developing successful synthetic lubricantssince entirely different side effects are likely to occur under the moreextreme conditions to which synthetic lubricants are subjected.

According to the invention, a synthetic ester lubricant having excellentoxidation stability comprises a major amount of a synthetic esterlubricating oil and minor amounts, sufficient to increase the oxidationstability of the oil, of (1) a substituted phenothiazine having theformula 3,6 42,fi3 Patented Feb. 15, 1972 wherein R is selected from thegroup consisting of alkyl, aryl, alkaryl, aralkyl and cyanoalkylradicals having from 1 to 12 carbon atoms, and R R R and R are selectedfrom the group consisting of hydrogen and alkyl and alkyoxy radicalshaving from 1 to 12 carbon atoms; and (2) a substituted triazineselected from the group consisting of symmetrical triazines andasymmetrical triazines having the respective formulas X{ HY XI N N and Jwherein X, Y and Z are selected from the group consisting of NH C to Chydrocarbylamino, di-C to C hydrocarbylamino, pyridylamino,di-pyridylamino, C to C hydrocarbyl and pyridyl, and wherein at leastone X, Y or Z substituent is an amino grouping, the nitrogen atom ofwhich is attached to the heterocyclic ring.

The N-su-bstituted phenothiazines preferably have one alkyl or alkoxyradical as substituent in each aromatic ring comprising thephenothiazine molecule and 3,7-substitution is most preferred.Preparation of N-substit-uted p'henothiazines is described, for example,in British patent specification No. 873,066. N-substitutedphenothiazines which are particularly useful for the purposes of thepresent invention are N-methyl-3,7-dioctyl phenothiazine,

N-n.butyl-3,7-dioctyl phenothiazine, N-n.octyl-3,7-dioctylphenothiazine, N-phenyl-3,7-dioctyl phenothiazine, N-tolyl-3,7-dioctylphenothiazine, N-cyanoethyl-3,7-dioctyl phenothiazine,N-cyanopropyl-3,7-dioctyl phenothiazine, N-cyanobutyl-S,7-dioctylphenothiazine, N-benzyl-3,7-dioctyl phenothiazine, N-benzyl-3,7-dibutylphenothiazine, N-benzyl-3,7-diisopropoxy phenothiazine,N-benzyl-3,7-dibutoxy phenothiazine and mixtures thereof.

It is anticipated that a wide range of triazine compounds may be used inconjunction with the phenothiazines for the purpose of the presentinvention, the choice of substituents being limited by requirements ofsolubility in the ester. It is envisaged that the triazines giving thebest combination of solubility and activity will be those having thegeneral formulae as follows- Types 1, 2 and 3 are 1,3,5-triazinesreferred to as symmetrical or s-triazines.

R R. R3

\ I Re i N R Rs R N N R4 Typc7 Types 4 to 8 are 1,2,4-triazines referredto as asymmetrical or as-triazines.

R may be H, C C hydrocarbyl, or pyridyl R may be H, C -C hydrocarbyl, orpyridyl R may be H, C C hydrocarbyl, or pyridyl R may be H, C -Chydrocarbyl, or pyridyl R may be H, C C hydrocarbyl, or pyridyl R may beH, C C hydrocarbyl, or pyridyl R to R may be C to C hydrocarbyl, C to Chydrocarbylamino, pyridyl or pyridylamino, where the term hydrocarbyl isintended to mean a radical formed from a hydrocarbon by removal of ahydrogen atom. All hydrocarbyl groups within the claimed ranges whichare free of aliphatic unsaturation are operable, whether they are alkyl,aryl, alkaryl, aralkyl, cycloalkyl, single or multi-ring, straight chainor branched.

Type 8 Examples of triazines which may be used in accordance with theinvention are as follows:

2-a1nino-4-anilino-6-benzylamino-1,3,5-triazine2-amino-4-anilino-6-dibutyl amino-1,3,5-triazine2-arnino-4-anilino-6-benzylamino-1,3,5-triazine 2-azido4-ethylamino-6-t-butyl amino-1,3,5-triazine 2-di isobutylamino-4-octadecylamino-6-phenyl- 1,3,5-triazine 2,4-di-n-butylamino-6-anilino-1,3,5-triazine2-benzylamino-4,6-dianilino-1,3,5-triazine 2-amino-4-butylamino-6-phenyl-1,3,5-triazine 2-amino-4,6-di-anilino1,3,5-triazine3-amino-5,6-di-phenyl-1,2,4-triazine2-amino-4-n-butylamino-6-phenyl-1,3,5-triazine 2-diisobutylamino-4-dodecyl-amino-6-pheny1- 1,3,5-triazine2,4-bis(n-butylamino)-6-phenyl-1,3,5-triazine 2-cyclohexyl-4-hexadecylamino-6-(di-n-butylamino)- 1,3,5-triazine2-amino-4-sec-butylamino-6-phenyl-1,3,5-triazine2,4-bis(di-n-butylamino)6-N-cyano-ethylamino- 1,3,5-triazine2,4-bis(sec-butyl amino)-6-phenyl-1,3,5-triazine Z-methyloctylamino-4,6-bis(di-n-butylamino)- 1,3,5-triazine2,4,6-tris(n-butylamino)-1,3 ,S-triazine 2-anilino-4,6-bis (ethylamino)-1,3,5-triazine 2-anilino-4,6-bis(n-butylamino)-1,3,5-triazine2-phenyl-4- (di-n-butylamino) -6-octadecyl amino- 1,3,5-triazine2-n-butylamino-4,6-dianilino-1,3,5-triazine 2-dioctylamino-4,6-bis(diethylamino)-1,3,5-triazine 3-amino-5,6-diphenyl-1,2,4-triazine5-amino-3,6-diphenyl-1,2,4-triazine 6-amino-3,5-diphenyl-1,2,4-triazine3,5-bis(amino)-6-phenyl-1,2,4-triazine3,5-bis(n-butylamino)-6-phenyl-1,2,4-triazine 5,6-bisamino-3-pheny1-1,2,4-triazine It is as yet not fully understood by whatmechanism the triazine compounds act in improving the antioxidant effectof the phenothiazines, but it is thought that the triazine compoundsexhibit metal deactivating or passivating properties as well as behavingas antioxidants.

Preferably the phenothiazines and triazines of the present invention areeach employed in a proportion of 0.005 to 10% by weight, more preferablyin a proportion of 0.01 to 5% by weight based on the whole composition.

Esters suitable as the ester base in the composition of the presentinvention are simple esters, complex esters, polyesters or mixturesthereof to which may be added thickeners, depending upon the viscometricproperties desired for the composition and the temperature conditionsunder which it is to be used. By simple ester is meant an ester formedbetween an aliphatic dicarboxylic acid and an aliphatic monohydricalcohol, preferred simple esters being formed from an aliphaticdiscarboxylic acid containing from 6 to 10 carbon atoms in the moleculeand a branched chain monohydric alcohol containing from 6 to 12 carbonatoms in the molecule, especially those alcohols having no hydrogen onthe beta carbon atom. Examples of simple esters useful for the purposesof the present invention are diiso-octyl sebacate, di(2-ethyl hexyl)sebacate, diiso-octyl azelate, diisodecyl azelate, di- (3,5,5-trimethylhexyl) adipate, 2-ethyl hexyl 3,5,5-trimethyl hexyl sebacate and2,2,4-trimethyl pentyl azelate.

By complex ester is meant an ester formed from various combinations ofan aliphatic dicarboxylic acid, a glycol or polyglycol and either orboth of an aliphatic monohydric alcohol and an aliphatic mono-carboxylicacid. Some typical complex ester structures are represented by A(DG),,Mand MG(DG) M wherein A, D, G and M represent the esterification residuesfrom an aliphatic monohydric alcohol, an aliphatic dicarboxylic acid, aglycol or polyglycol and an aliphatic monocarboxylic acid respectivelyand n is a number from 1 to 6. Examples of typical starting materialssuitable for the preparation of such esters are 2-ethyl butyl alcohol,2-ethyl hexyl alcohol, caproic acids, pelargonic acid, capric acid,neopentyl glycol, ethylene glycol, propylene glycol, polyglycols such aspolyethylene glycols, sebacic acid, adipic acid, azelaic acid andpimelic acid.

By polyesters is meant esters made from aliphatic alcohols havingtherein at least 3 hydroxyl groups, for example esters made fromtrimethylol propane, e.g. trimethylol propane, tripelargone, tetraesters such as the pentaerythritol tetra esters or the dimers or trimersof the same and dipentylerythritol esters, for example esters sold underthe Registered Trademarks Hercolube A and Hercolube F, all esters beingfatty acid esters. Preferably each fatty acid radical of the estercontains from 4 to 18 carbon atom and more preferably from 6 to 14carbon atoms.

As thickeners there may be used polymers of esters of acrylic or analkyl substituted acrylic acid, for example lauryl methacrylate, or anether or a polyoxyalkylene glycol of the general formula R O(R O),,Rwherein R is an alkyl group, R is hydrogen or an alkyl group, R is analkylene group of 2 to 4 carbon atoms and n is a number greater thanunity. Suitable compounds are marketed under the registered trademarkUcon, specific examples being LB 385, LB 525, LB 625. Also suitable arecopolymers of propylene oxide and ethylene oxide marketed under theRegistered Trademark Oxilube, e.g. Oxilube 140. The thickeners may beused in proportions up to 40% by weight calculated on the finallubricant composition depending upon the viscometric properties requiredfor said lubricant.

The ester base compositions of the present invention may additionallycontain extreme pressure additives, additional antioxidants, metaldeactivators, anti-corrosion agents, anti-foaming agents, dye stuffs andother additives known to be suitable for use with ester base lubricantformulations.

As examples of extreme pressure additives are mentioned esters of acidsof phosphorus particularly triphenyl phosphorothionate, tritolylphosphorothionate and trixylyl phosphorothionate; phosphate esters e.g.triphenyl phosphate and tritolyl phosphate may also be used. Anotherclass of phosphorus containing extreme pressure additives which may beusefully employed in the ester base compositions of the presentinvention are diaryl haloalkyl phosphates which are described andclaimed in British Pat. No. 1,035,984. Yet another class of extremepressure additives which may usefully be employed in the present estercompositions are the chlorinated dior polyphenyls i.e. diphenyls,terphenyls, higher polyphenyls or mixtures thereof containing at leastone chlorine atom attached directly to each benzene nucleus for examplechlorinated dior poly-phenyls sold under the Registered TrademarkArochlor. Still another suitable class of extreme pressure additives forthe present use are substituted oxetane polymers, i.e. polymers preparedfrom oxetanes having the formula:

X CH:

wherein one X is chlorine or bromine and the others are chosen fromhydrogen, chlorine or bromine e.g. 3,3-bis (chloromethyl) oxetane.Further information concerning oxetane polymers may be found in UK. Pat.No. 964,672.

A class of extreme pressure additives which are particularly useful forconferring extra resistance to extreme pressure conditions are the monochloro methyl phosphonic acid salts of tertiary alkyl primary amines,for example, the mono chloro methyl phosphonic acid salts of C tertiaryalkyl primary amines.

Additional anti-oxidants suitable for use in compositions of the presentinvention are alkylated phenols e.g. 2,6-ditertiary butyl-4-methylphenol and alkylated bis phenols e.g. 4,4'-methylene bis (2,6-ditertiarybutyl phe- 1101).

As metal deactivators and or passivators and corrosion inhibitors whichmay be employed in compositions according to the present invention theremay be used a wide range of compounds which can be employed according tothe metal or metals with which the compositions will come into contact.Materials particularly suitable when the metals to be contacted arecopper, copper alloy or silver are the triazoles, e.g.1,2,3-benztriazole, methyl- 1,2,3 benztriazole,3-amino-5-methyl-1,2,4-triazlole, especially3-amino-5-phenyl-1,2,4-triazole, 3-amino-5-p-yridyl- 1,2,4-triazole,3-amino-5-anilido-1,2,4-triazole and 5,5'-diamino3,3'-bi-(1,2,4-triazole), up to about 1% preferably about 0.5% wt. ofthese materials being useful. Also useful when the metals are copper,cadmium, silver and magnesium for example, are similar weights ofpyridylamines, particularly di pyridylamines, e.g. 2,2-dipyridylamine.Small proportions e.g. from 0.01 to 0.2% wt. of sebacic, azelaic oradipic acid are also useful additives for the protection of lead whilemetal petroleum sulphonates are useful rust inhibitors.

Suitable anti-foaming agents are the poly-dirnethyl siloxanes havingviscosities from 100 to 100,000 c./s. at C.

The lubricant compositions of the present invention are furtherillustrated by the following examples which are not intended to limitthe invention to the particular compounds or compositions described.

EXAMPLE I To illustrate the efiicacy of the additive combination of theinvention the following compositions were prepared and subjected to theRolls Royce Blown Oxidation Test. In this test, 250 ml. per minute ofair saturated with water vapor, are bubbled under controlled conditionsthrough a 50 gram sample of ester base composition. Deterioration of thecomposition due to oxidation is then measured in terms of tolueneinsolubles, volatility, change in kinematic viscosity (VK) and increasein acidity...Test conditions and results are presented in Table I. Thebase stock employed in the preparation of all of the compositions shownwas a mixture of approximately 70% by weight of Hercolube A(pentaerythrityl esters of saturated fatty acids of C average chainlength) and by weight Hercolube F (dipentaerythrityl esters of saturatedfatty acids of C average chain length).

TABLE I Rolls Royce a blown oxidation test (1001): Conditions 192 hrs.at 225 0 Change in VK at Toluene Volatility 210 F., Increase inComposition insolubles, los percent acid value, number percent wt.percent wt. increase mg. KOH/g.

l Solid 2 Solid 3 0.20, 0. 23 40, 41 +35, +40 1.15, 1.80

B The words Rolls Royce" are a registered trademark.

The data presented in Table I are indicative of the surprising resultsobtained by use of the additive combination of the invention.

Compositions 1 and 2 containing each of the additives separately,completely solidified under the extreme conditions of the test. Incomparison composition 3 containing the additive combination of theinvention displayed remarkable oxidation stability.

EXAMPLE II To further demonstrate the effectiveness of the ester basecompositions of the invention, a series of formulations containing thephenothiazine-triazine additive combination were compared tocompositions containing a well known prior art antioxidant in place ofthe triazine. These formulations and test results are shown in Table II.The base stock employed in preparing these compositions was the same asthat used in Example I.

Composition 4-Base stock plus 1.7% wt. N-benzyl 3,7- dioctylphenothiazine and 1.5% wt. phenyl-alpha-naphthylamine Composition 5-Basestock plus 1.7% wt. N-benzyl 3,7- dioctyl phenothiazine and 2.0% wt.phenyl-alpha-naphthylamine Composition 6-Base stock plus 1.7% wt.N-benzyl 3,7- dioctyl phenothiazine and 2.0% Wt.2-azido-4-ethylamino-6-t-butylamino-l,3,5-triazine.

Composition 7-Base stock plus 1.7% wt. N-benzyl 3,7- dioctylphenothiazine and 2.0% wt. 2-amino-4-butylamino-6-phenyl-l,3,5-triazineComposition 8Base stock plus 1.7% wt. N-benzyl 3,7- dioctylphenothiazine and 2.0% wt. 2 amino-4,6-dianilino-1,3,5-triazineComposition 9--Base stock plus 1.7% wt. N-benzyl 3,7- dioctylphenothiazine and 2.0% wt. 3-amino-5,6,-diphenyl-l,2,4-triazineComposition 10-Base stock plus 2.0% wt. N-benzyl 3,7- dioctylphenothiazine and 1.0% wt. 2-benzylamine-4,6- dianilino-1,3,5-triazineComposition l1Base stock plus 2.0% wt. N-benzyl 3,7- dioctylphenothiazine and 1.0% 2-anilino-4,6-bis (ethylamino)-1,3,5-triazineComposition 12Base stock plus 2.0% N-benzyl 3,7-dioctyl phenothiazineand 1.0% 2-amino-4-anilino-6-benzylamine-l,3,5-triazine TABLE II RollsRoyce blown oxidation test (100): Conditions 192 hrs. at 225 C.

Toluene Volatility Change in Increase in Composition insolubles, loss,VK at acid value, number percent wt. percent wt. at 210 F., mg. KOH/g.

From Table II it is clear that although the formulations of theinvention give slightly greater toluene insoluble values, they aresignificantly superior to the compositions containing the prior artantioxidant in respect to the classical oxidation stability factors suchas increase in acid value and 210 F. VK change.

EXAMPLE III In order to illustrate still further the superior oxidationstability characteristics of formulations according to the presentinvention, several of the compositions were subjected to a modifiedversion of the above test wherein the oxidation is carried out at 250 C.for 22 hrs. The results of this series of tests is given in Table III,wherein the most important factor, the percent change in viscosity at100 F. is compared.

TABLE III Blown oxidation test: 22 hrs. at 250 C.

Composition No.: Percent change in VK at 100 F.

We claim as our invention:

1. A lubricant composition comprising a major amount of a syntheticester lubricating oil and a combination of 0.005 to 10% Wt. each of (l)a substituted phenothiazine having the formula wherein R is selectedfrom the group consisting of alkyl, aryl, alkaryl, aralkyl andcyanoalkyl radicals having from 1 to 12 carbon atoms, and R R R and Rare selected from the group consisting of hydrogen and alkyl and alkoxyradicals having from 1 to 12 carbon atoms; and

(2) a substituted triazine selected from the group consisting ofsymmetrical triazines and asymmetrical triazines having the respectiveformulas to 5% by weight.

3. The composition of claim 1 wherein the substituted 20 phenothiazineis an N-substituted 3,7-dialkyl phenothiazine.

4. The composition of claim 3 wherein the triazine is 3. 1,3,5 triazine.

5. The composition of claim 3 wherein the triazine is 9. 1,2,4 triazine.

6. The composition of claim 4 wherein the substituted phenothiazine isN-benzy1-3,7-dioctyl phenothiazine.

7. The composition of claim 5 wherein the substituted phenothiazine isN-benzyl-3,7-dioctyl phenothiazine.

References Cited UNITED STATES PATENTS 3,344,068 9/1967 Waight et al.252-47 3,093,585 6/1963 Low et al 25251.5 X 3,378,490 4/1968 Hotton252-50 X 3,498,981 3/ 1970 Culbertson 25250 X DANIEL E. WYMAN, PrimaryExaminer W. H. CANNON, Assistant Examiner US. Cl. X.R. 252-47, 51.5 R

